Introduction: Critically-ill patients with ST-segment elevation myocardial infarction (STEMI) often present with insufficient gastroduodenal motility, liver hypoperfusion, and higher levels of circulating catecholamines. All of these factors can lead to reduced efficacy of clopidogrel, which is only available as a p.o. medication. The aim of the study was to compare clopidogrel effectiveness in unstable STEMI patients on mechanical ventilation with stable STEMI patients.
Materials and methods: Two groups of twenty patients with STEMI were enrolled. One group (unstable) consisted of 20 hemodynamically unstable patients on mechanical ventilation and catecholamine support. The other group (stable) consisted of 20 control patients (all patients with STEMI in Killip I class). All patients were treated by primary Percutaneous coronary intervention. Blood samples were drawn before (baseline), at 4h (4h+), 24h (1d+) and 2 days (2d+) after clopidogrel administration. Clopidogrel efficacy was assessed by measurement of vasodilator-stimulated phosphoprotein phosphorylation index.
Results: The decrease in the vasodilator-stimulated phosphoprotein (VASP) index was substantially less in unstable patients compared with stable ones (ANOVA, P < 0.001). In stable patients, the VASP index decreased significantly by 20% at 4h+ and by 34% at 1d+, and remained significantly decreased by 31% at 2d+. In unstable patients, the VASP decreased nonsignificantly by 8% at 4h+, and no further decrease of VASP was present (-7% at 1d+, -11% at 2d+).
Conclusions: Laboratory clopidogrel efficacy is lower in patients with MI and severe hemodynamic instability, probably due to splanchnic and liver hypoperfusion and catecholamine use.